High-frequency surface hardening



June 27, 1950 H. GRUMEI. 2,512,718

HIGH-FREQUENCY SURFACE HARDENING Filed Nov. 2, 1945 2 Sheets-Sheet l Ihre for Hawk! Gel/MEL June 27, 1950 H. GRUMEL HIGH-FREQUENCY SURFACE HARDENING Filed Nov. 2, 1945 20 f6 8a 9a /7\ 23 fn l1 2 Sheets-Sheet 2 [hue/:for HENRI GRUMEL 6 mmf@ forneys Patented June 27, 1950 HIGH-FREQUENCY SURFACE HARDENING Henri Grumel, Paris, France, assignor to Societe Francaise Radio Electrique, a corporation of France Application November 2, 1945, Serial No. 626,270 In France March 30, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires March 30, 1963 7 Claims. 1

`This invention relates to new and useful improvements in apparatus for high frequency induction surface hardening `and more particularly forthe mass production surface hardening of articles of small dimensions.

Objects `and advantages of the invention will be set forth in part hereinafter and will in part be obvious herefrom, or may be learned by practice with the invention, the same being realized and attained by means of the instrumentalities and combinations set out in the appended claims.v

@The invention consists in the novel parts, constructions, arrangements and combinations herein described and shown.

The annexed drawings, referred to herein and constituting a part hereof, illustrate an embodiment of the invention and, with the description, serve to explain the principles thereof.

In said drawings:

Figure 1 is a side elevation of the apparatus embodyingr the invention;

Figure 2 is a plan view;

Figure 3 is a sectional elevation on the line A-B of Figure 2 showing the apparatus mounted on a high frequency generator of the type above referred to;

Figure 4 is a sectional plan taken on line C-D of Figure 1;

Figure 5 is a detail section of the 'casing taken online E-F of Figure 1;

Figure 6 is a diagram of the high frequency electric circuit; and

Figure 7 is a diagram of part of the quenching fluid circuit.

' Surface hardening of articles of small dimension by induction, in the case of mass production, must be carried out, by reason of the capacity of production of the plant, at an extremely rapid rate, often much higher than the needs of the producer. Thus, in order to permit of a rational utilisation of the generators supplying the high frequency, it is necessary to operate on various different kinds of articles in alternate series.

. It is -an object of the invention, in order to reduce loss of time in changing from one kind of article to another, to provide tools adapted to the treatment of each of such articles and capable of being very rapidly mounted on the generator and without delicate mechanical adjustments being necessary.

'Io this end, according to the invention, there is provided for each type of article to be treated, a detachable monobloc or single piece mounting device comprising a support on which are directly mounted the heating inductor, the liquid spraying devices for surface hardening andA possibly the mechanism for producing movement of the articles during the various stages of treatment, arrangements being provided to permit the convenient attachment of the fitment on the generator as well as the ready attachment of the electric connections, water pipes, and mechanical drive connections between the detachably mounted ftment and the elements which are permanently xed on the generator.

The high frequency generator described in the French Patent filed on December 1, 1942, for Valve installation for the thermal treatment of metals by high frequency is particularly adapted to supply such assemblies.

The embodiment of the single piece tment thus defined may be very varied, depending on the shape of the article to be hardened. By way of non-restrictive example, there will now be described a fitment suitable for the heat treatment of articles of revolution of which the length of the part to be treated is not greater than the diameter, the article shown in the case of this example being a swivel joint.

Referring now specifically to the embodiment of the invention illustrated in the drawings and as specifically shown in Figures 1 to 4, I is a cylindrical casing forming the body of the apparatus, said casing being detachably fixed on the front plate 5I of a high frequency generator through the intermediary of a bracket 2. Within the casing there is arranged a mandrel 3 by which the article 4 to be treated is supported. The mandrel is mounted on a hollow shaft 5 adapted to be driven from any convenient source through a pulley wheel 6 or a corresponding sprocket wheel. This arrangement provides for rotation of the article during treatment in order that the profile of the part to be tempered may be accurately determined.

A rod I axially slidable within the interior of the hollow shaft 5 is provided to facilitate the removal of the articles `after treatment.

The shape of the article to be heat treated as here shown makes it necessary to employ an inductor which opens to permit insertion and removal of the article. Accordingly, the inductor is formed of two semi-cylindrical members or halfshells 8a and 8b respectively carried by current supply arms 9a and 9b which are supported by pairs of upper and lower pivots 10a, IIa and IUb, I Ib respectively. These pivots are carried by insulating transverse bars I2 and I3 which are in turn supported by uprights I4a yand I4b rigid with the casing I.

The electrical connection of the arms 9a and scribed it is necessary to providej iornelectrical contact between the semi-cylindricalmembers or jaws 8a, 8b. It is very cliiilcult,l `iffnot impossible,

oi the inductor. Consequently, a pair of silver contact points or pips I are provided Onsaid jaws intermediate the upper and lower edges`- thereof, as shown in Figures 3 .and this arf--` .10, to provide a good contact over the whole height rangement permitting accurate closingy offi the.-

electrical circuit and strictly identical operating conditions at all times. As with this arrangement the density oi the current, however, is greatly increased inthe central Zone of the vinductor,`

which might cause over-heating in the central part oi the article being treated, v the current supply arms ta and b are oi trapezoidal or equivalentiiorin and constructed in such manner that at the point or" attachment to the conductor, the

current density is, on the contrary, much greater at the top and at the bottom than towards the centre. This condition, as will be easily understood, arises from the characteristicV transmission off-.high frequency currents in conductorsl tending to; become concentrated at surfaces and edges. This-eiiect as produced in the arrangement ofv the invention can thus be .compensated in conjunction with the rotation of the article during the treatment, which ensures heating over the whole-,oi thesuriace being treated.

The two inductor jaws Ba` and 8b are kept in contact, during the operations ci heating and tempering, by a magneti-c device'generally indicatedat il. The magnetic 'circuit of: this device is constituted by two cores i3 and I9 rigidly iixedA on a casing 2Q of non-magnetic metal and inte-` gral. with the central case I,-and by two yokes 21a and-2 ib respectively integral with the jaws 3a and` fila-'oi the inductors. The casing 2Q, in addition tosupporting the cores, protects the coils 22 and 23.- frcmthe jets of water during the hardening operation.

The yokes Zia and 2lb are xeclon arms 24a and 24h-by meansof hinged joints allowing them to. align with the ends oi the coresla andr It. The

arm 2da, is rigid with with the member ta, whichcorrect `closing lposition pared with that oi the secondary circuit. This impedance serves to determine the potential of the current with respect to earth when the heating inductor is not earthed; it is of sufficient value to ensure that if, on the contrary, it should be advantageous to earth the central point of the inductor, the circulation current which may red trol magnetic device I'I. In this way, the central point of the inductor is earthed without inconvenience through the intermediary of the device Il when the inductor is closed.

The hardening liquid is admitted to the casing I through a nozzle 26, whence it passes from the top to the bottom between the inductor members 8a: and 8b. and the part of the article l being treated. To ensure a good hydraulic joint between the inductor shells and the casing I the latter terminates in a metallic collar 2'! in which there is provided a rubber ring 23 of circular cross-section. The inductor parts each have a projecting rim -or lip 29 which engages this ring when the inductors'are `in the working position.

In A-order that when the heating operation ceases, a very rapid delivery of water is provided tot the' part being treated, the casing I is kept permanently full of water. To this end, an electrically. operated valveV which controlsthey supply of water isvby-passed, as shown in Figure '7, by a small gauge pipe C through which therecontinuously passes a stream of water to compensate or leakage. The water is thusniain-y tainedV in the casing l to the level m--n, being the level oi an over-flow port in the casing.A Iir the-normal delivery of hardening water, the leak-- age represented by this hole and by that of the gap between the inductor jaws, is absolutelyA negligible.

It will be noticed that in order to avoid induced circulation currents in the casing I, the latten is split at til from the top to the bottom. A rubberjoint 3i (see also Figure 5) ensures thatthis slit is tightly closed against the passage of water; Figure 5 giving a section of the casing, clearly shows this arangeinent.

It is to be understood that the foregoing `description of an embodiment of apparatus accordsult from lack of electrical symmetry in the system-ds of negligible value. This arrangement is employed in the construction here shown and described, no insulation being thereforenecessary between the` inductor member 8a, bfandgtheconing to this invention is purely exemplary thereof and numerous modincations may be made therein without departing :from the spirit or" the invention.

I claim:

1. In a high frequency induction current heating apparatus, an inductor composed of two solid half-shells similar and oppositely disposed separated by a small interval and together forming a cavity capable of receiving the piece to be heated, a contact in the form of a plug with a small predetermined suriace being Xed between the'edges of the half-shells at a mid-height of saidhalfshells, lead-in arms for high frequency current connected to said half-shells at the edges thereof opposite to those which have the aforesaid con-V tact, said arm being of a substantially trapezoidalform and constructed and arranged so as to ob tain a stronger current density toward the-top and bottom of said shells than toward their mi'dt portion, means enabling the two half-shells to be firmly secured to each other in the zone of their contact, means enabling the separation of the two half-shells from each other or to be brought together in their normal working position, a support for holding the piece to be heated inthe cavity of the inductor so that the axis of the piece and of the inductor coincide, and meansA for Causing the said piece to rotate about said axis;

2. Heating apparatus according to claim 1,

wherein the means for securing the half-shells opposite each other comprises an electromagnet:

and a compression spring.

3. Heating apparatus according to claim` l1, wherein themeans enabling the separation of. the twoz-half-shellsV or of bringing them togetherwatt` their normal working position comprises a pivoted support.

4. In an apparatus for heat treating small pieces by high frequency induction currents and having a generator and a transformer secondary, the combination of a heating unit having an attached supporting frame readily detachable from said generator and means thereon rotatable about an axis and carrying the piece to be heated, said heating unit comprising two opposed jaws carrying respective parts of an inductor and having in their opposed faces hollowed-out surfaces producing therebetween a substantially spherical cavity, and having upper and lower edges in planes normal to said axis, supporting and current supply means for said inductor comprising current-carrying arms, said arms at one end connected to said. jaw and inductor parts respectively and at the other end mounted on pivots respectively extending substantially parallel to said axis, said arms having a progressively increasing dimension parallel to said axis from their ends joining the jaws to their pivots, said jaws having a pair of Contact studs electrically connecting the same when in closed position at a point opposite to the pivoted ends of the jaws and in a plane perpendicular to said axis and medial of the jaws, means for clamping the jaws together, and means for rotating said piece whereby during heating and rotation the tendency of the heating currents due tc said edges and said dimension to follow lines causing unequal density distribution is compensated.

5. In an apparatus for heat treating small pieces by high frequency induction currents and having a generator and a transformer secondary, the combination of a heating unit having an attached supporting frame readily detachable from said generator and means thereon rotatable about an axis and carrying the piece to be heated, said heating unit comprising two opposed jaws carrying respective parts of an inductor and having faces with shapes adapted to the form of the element to be heated, and having upper and lower edges in planes normal to said axis, supporting and current supply means for said inductor comprising current carrying arms, said arms at one end connected to said jaw and inductor parts re-` spectively and at the other end mounted on pivots respectively extending substantially parallel to said axis, said arm having a progressively increasing dimension parallel to said axis from their ends joining the jaws to their pivots, said jaws having a pair of contact studs electrically connecting the same when in closed position at a point opposite to the pivoted ends of the jaws and in a plane perpendicular to said axis and medial of the jaws, means for clamping the jaws together, and means for rotating said piece whereby during heating and rotation the tendency of the heating currents due to said edges and said dimensions to follow lines causing unequal density distribution is compensated, said combination, including means for determining the potential of the heating current with respect to earth comprising an impedance of high value respecting that of the secondary circuit and connected between the center of the secondary circuit opposite the location of the inductor connection and ground.

6. The combination according to claim 5, in which the means for clamping the jaws together comprises an electromagnet and means for mounting it on said unit support without insulation therebetween and the inductor parts.

7. In an apparatus for heat treating small pieces by high frequency induction currents and having a generator and a transformer secondary, the combination of a heating unit having an attached supporting frame readily detachable from said generator and means thereon rotatable about an axis and carrying the piece to be heated, said heating unit comprising two opposed jaws carrying respective parts oi an inductor and having faces with shapes adapted to the form of the element to be heated, and having upper and lower edges in planes normal to said axis, supporting and current supply means for said inductor comprising current carrying arms, said arms at one end connected to said jaw and inductor parts respectively and at the other end mounted on pivots respectively extending substantially parallel to sai-d axis, said arm having a progressively increasing dimension parallel to said axis from their ends joining the jaws to their pivots, said jaws having a pair oi contact studs electrically connecting the same when in closed position at a point opposite to the pivoted ends oi the jaws and in a plane perpendicular to said axis and medial of the jaws, means for clamping the jaws together, and means for rotating said piece whereby during heating and rotation the tendency of the heating currents due to said edges and said dimensions to follow lines causing unequal density distribution is compensated, said combination, including means to reduce circulation currents arising from lack of electrical symmetry in the system when the jaw control point is grounded, comprising an impedance of high value respecting that of the secondary circuit and connected between the center of the secondary circuit opposite the location of the inductor connection and ground.

HENRI GRUMEL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,059,300 Adams Nov. 3, 1936 2,180,038 Denneen et al NOV. 14, 1939 2,181,899 Kennedy Dec. 5, 1939 2,240,493 Denneen May 6, 1941 2,255,103 Denneen et al Sept. 9, 1941 2,266,176 Denneen et al Dec. 16, 1941 2,280,064 Denneen et al Apr. 21, 1942 2,282,322 Denneen et al May 12, 1942 2,288,034 Somes June 30, 1942 2,308,788 Somes Jan. 19, 1943 2,368,809 Denneen et al. Feb. 6, 1945 2,416,742 Farr Mar. 4, 1947 FOREIGN PATENTS Number Country Date 467,308 Great Britain June 15, 1937 

